Biomechanics of horizontal meniscus tear and healing during knee flexion: Finite element analysis

Meniscus horizontal tear is a common injury that mostly occurs in middle-aged and elderly people, and the effect of repair surgery directly affects the functional recovery of the knee joint and prevention of degenerative joint diseases. However, the stress concentration in a horizontal tear is not well understood. The primary objective of this study was to examine the reparative mechanisms involved in addressing horizontal tears of the meniscus and to elucidate the alterations in mechanical behavior throughout the subsequent postoperative healing stages. Based on clinical MRI scan data of normal human knee joint, an accurate three-dimensional finite element model of the knee joint was established to simulate the meniscus at different states: including complete, horizontal torn, repaired and at different degrees of healing. An animal model was established to conduct in vitro loading experiments to assist in validating the model. Static standing simulation revealed the phenomenon of stress concentration in the area of horizontal tears. Knee flexion simulations identified the risk of tear propagation at the endpoints of the horizontal tear. Following suture repair and progressive healing, stress concentration was observed at the site of sutures, while the stress levels decreased at the endpoints of the horizontal tear. As healing progressed, the mechanical function of the meniscus gradually recovered. During progressive healing, the changing trends can provide a reference for patients' postoperative recovery activities. This finding has important implications for guiding clinical treatment strategies and rehabilitation plans for meniscal tears.